The object of the invention is a method for cutting trees in the vicinity of a power line.
Land areas in the vicinity of power lines must be kept free of trees, as it is thus possible to prevent line damage caused by trees that might touch the electricity wires and disturbances in power distribution caused thereby. However, as trees tend to grow particularly fast especially in open power line areas, power lines must be cleared regularly by cutting trees that have grown too close to the electricity wires. According to a known method, trees are cut manually using a power saw, for example. Manual work is, however, arduous and very slow. In addition, when trees are cut with a power saw, the whole tree often has to be felled, even though it would be sufficient to cut only the top of the tree to prevent the tree from touching the electricity wires.
The aim of the present invention is to achieve a new method for cutting trees that are in the vicinity of a power line. It is characteristic of the method relating to the invention that the tops of the trees are cut using a topping saw suspended from a helicopter in such a way that the helicopter is flown in the direction of the power line so close to the electricity wires that the topping saw suspended from the helicopter cuts the desired treetops.
By the method relating to the invention it is possible to cut the tops of the trees growing in the area of a power line at the desired distance from the electricity wire of the power line. By using the helicopter it is possible to move fast and at the same time to achieve the desired sawing line in order to achieve a clear strip of the desired size in the vicinity of the electricity wires.
According to a preferred embodiment of the method relating to the invention the tops of the trees are cut with a topping saw suspended from a helicopter, the saw comprising a motor and two cutting blades that rotate in the same direction.
According to a second preferred embodiment of the method relating to the invention the cutting line of the topping saw attached to the helicopter is determined in such a way that the helicopter is flown so that the sighting device incorporated in the topping saw is directed towards the electricity wire of the power line.
According to a third preferred embodiment of the method relating to the invention the cutting line of the topping saw attached to the helicopter is determined with the help of a video camera attached to the suspension bar for the topping saw, in such a way that the helicopter is flown with the help of a monitor placed in connection with the helicopter""s cockpit, the video camera being directed towards the electricity wire of the power line.
According to yet another preferred embodiment of the method the upper limit of the area where trees are to be cut is formed at an angle of 45xc2x0 in relation to the horizontal plane, in such a way that the video camera is attached to the suspension bar for the topping saw at an angle of 45xc2x0, and the helicopter is flown with the video camera directed towards the electricity wire of the power line and that the distance from the electricity wire of the point where trees are to be cut is determined by adjusting the distance of the video camera from the cutting blade of the topping saw.
Another object of the invention is a topping saw for cutting trees which are in the vicinity of a power line. It is characteristic of the topping saw relating to the invention that the topping saw comprises at least one cutting blade for cutting the tops of the trees, which cutting blade most preferably rotates in the direction of the horizontal plane, and that the topping saw is suspended from a helicopter by means of an intermediate element.
According to a preferred embodiment of the topping saw relating to the invention the topping saw comprises two cutting blades that are mainly horizontal and rotate in the same direction, and a motor that rotates the cutting blades.
According to a second preferred embodiment of the topping saw relating to the invention the topping saw comprises a sighting device which can be directed towards the electricity wire of the power line in order to determine the desired sawing line to be used when cutting the trees.
According to a third preferred embodiment of the topping saw, a video camera is attached to the suspension bar for the topping saw and there is a monitor in connection with the cockpit of the helicopter, with the help of which monitor the helicopter can be flown in such a way that the video camera is directed towards the electricity wire of the power line in order to achieve the desired sawing line.
According to yet another preferred embodiment of the topping saw, the video camera is attached to the suspension bar for the topping saw most preferably at an angle of 45xc2x0 so that the upper limit of the area where trees are to be cut also forms an angle of 45xc2x0 in relation to the horizontal plane, and that the distance of the video camera from the cutting blade of the topping saw can be adjusted in order to set the desired distance between the point where trees are to be cut and the electricity wire.